Is your PC still relying on an old-school hard drive? Installing a solid-state drive is the best upgrade investment you can make.

Installing an SSD in your PC, be it a laptop or a desktop, is one of the easiest and most effective ways to boost the machine's overall performance. The change won't be merely noticeable--it will startle you. Your system will boot more quickly, windows and menus will jump open, and programs and data will load much, much faster.

In case you don't know what an SSD is, the acronym stands for solid-state drive--that is, solid-state as in no moving parts, and drive as in the fact that an SSD appears as a hard drive to your computer. But instead of storing data on one or more spinning platters, an SSD writes and reads data to and from nonvolatile flash memory. In addition, an SSD contains a controller that's analogous to the memory controller in your PC's CPU or core-logic chipset.

Many vendors sell SSDs, but the devices are far from equal. Flash memory and controller technology have both advanced so quickly that what was fast last year is now second-class. The drives you might find in the bargain bin will be faster than a consumer-grade mechanical hard drive, but they won't deliver the astounding performance boost you'll be looking for after you read this article.

To get the skinny on state-of-the-art consumer SSDs, we brought seven drives from five vendors into the PCWorld Labs and put them through the wringer. We tested Corsair's Neutron and Neutron GTX drives; Kingston's HyperX 3K; OCZ's Vertex 4 and Vector drives; Samsung's 840 Pro; and the SanDisk Extreme. We also retested Intel's 240GB Series 335 SSD using our new benchmarking procedure (if you're curious, read our original review). Each drive delivers either 240GB or 256GB of storage, which is the current sweet spot in terms of price and performance. Each drive we tested proved to be a solid performer that will offer a significant boost over whatever conventional drive your machine has now. Some drives, however, are definitely faster than others.

If you'd like to upgrade a computer equipped with an older second-generation SATA interface (which maxes out at 3 gigbits per second), note that we also checked out the Apricorn Velocity Solo x2, an add-in card that upgrades any computer with an available PCIe 2.0 x2 slot to the newer SATA 6-gbps standard.

But before we dive into those reviews, here's a primer on SSDs that will tell you everything you need to know about this technology.

Controller

The memory/interface controller proved to be a major factor in determining each SSD's performance. Three of the drives we tested use a SandForce SF-2281 controller: the Kingston HyperX 3K, the SanDisk Extreme, and the Intel Series 335 (the controller firmware on this drive is tweaked to Intel's specifications). OCZ's Vector and Vertex 4 drives both use OCZ's proprietary IndiLinx controllers, namely the Everest 2 in the Vertex 4 and the Barefoot 3 in the Vector. Corsair is blazing a path with its Neutron series drives (the GTX and Neutron) by using Link A Media's LM87800 controller. Samsung's 840 Pro utilizes the company's proprietary MDX controller.

As you'll see in our performance chart, drives with the IndiLinx, Link A Media, and Samsung MDX controllers boasted significantly faster write speeds than the SandForce-based competition. In fact, counterintuitively, each of the five drives using those controllers wrote faster than they read. The SandForce-based drives were all good readers, but their comparatively slower write speeds dragged down their overall scores.

On the next page, I'll discuss memory types, interfaces, and how we measured performance.

Memory

Although the controller plays a big role in determining an SSD's performance, the type of flash memory inside an SSD is also a huge factor. The SSDs in this roundup used either synchronous or toggle-mode NAND.

You might also encounter the terms SLC (single-level cell),MLC (multi-level cell), and TLC (triple-level cell) when researching SSDs. An SLC NAND cell has two states--on or off--so it can store one bit of data. An MLC NAND cell has two states besides off, so it can store two bits of data, while a TLC NAND cell has three states in addition to off and is therefore capable of storing three bits of data.

While MLC and TLC NAND deliver more capacity in the same physical space, they also bring a trade-off in performance and endurance. SLC NAND is faster and more durable than the other two types, but it's also more expensive; you'll find it today only in enterprise-level drives. Very few drives use TLC NAND, because it's not as durable--it can't handle as many program/erase cycles (which I'll explain in a moment) as SLC and MLC can. Each of the drives in this roundup uses MLC NAND.

A note about endurance: All types of NAND flash memory have a limited life span. The MLC memory in consumer SSDs is good for 3000 to 10,000 P/E (program/erase) cycles, which is enough to deliver several years of normal usage. Unlike a mechanical hard drive, an SSD cannot simply write (program) data on top of old data that's no longer needed; once flash memory has been written to, it must be erased before it can be written to again. Newer SSDs running on modern operating systems (including Windows 7, Windows 8, Mac OS X 10.6.8, and Linux kernel 2.6.28) use the TRIM command (it's not an acronym, despite the caps) to actively inform the SSD controller of memory cells that contain unneeded data, so the controller can proactively erase those cells and make them available for storage once again.

So how long should you expect an SSD to last? The manufacturers' warranties provide a clue: Both of OCZ's drives, Corsair's Neutron drives, and Samsung's 840 Pro drives carry a five-year warranty; the rest of the drives we reviewed are warrantied for three years.

Interface

To take full advantage of a state-of-the-art SSD (that is, one with a third-generation SATA 6-gbps interface), and get close to the speeds you'll see in our benchmark charts, you'll need a motherboard with a third-generation SATA 6-gbps interface.

While mechanical hard drives don't come close to saturating the second-generation SATA 3-gbps bus, the latest SSDs are already bumping up the against the limit of third-gen SATA. If you're adding an SSD to a laptop that has only a SATA 3-gbps interface, save yourself some money and go middle of the road--you'll get very little benefit out of connecting a SATA 6-gbps drive to the older interface. If you're upgrading to an SSD on a desktop that has only a SATA 3-gbps interface, buy either a SATA 6-gbps controller card or a SATA 6-gbps piggyback card, such as the Apricorn Velocity Solo x2 (read our review). Under any circumstance, buy a top performer, and in the future you can transfer it into a better system to realize its full potential.

Performance

We evaluated the SSDs with a series of real-world data-transfer tests (by "real world," we mean a commonplace selection of data). Each drive was required to read and write both a 10GB mix of smaller files and folders and a single large 10GB file. To see just how fast the drives could go, we utilized a 16GB RAM disk to avoid any bottlenecks or interaction issues that a hard drive or second SSD might cause.

When it came to reading data, every drive we tested turned in good numbers. Oddly enough, the 256MB OCZ Vertex 4, which took fourth place overall with its combined reading and writing, was the slowest reader at 393.5 MBps (file mix and large file combined). The highest combined mark, on the other hand, wasn't tremendously higher: Samsung's 240GB 840 Pro delivered 450.8 MBps (about 14% faster).

Overall, the aforementioned Samsung 840 Pro and OCZ's 256MB Vector were the stars of the roundup, finishing first and second respectively. The 840 Pro delivered an overall combined read/write speed of 496.2 MBps, and the Vector delivered 489.1 MBps. The 840 Pro finished first in every test except for writing our mix of smaller files and folders, where the Vector bested it. The Corsair Neutron GTX (240GB) placed third with a speed of 459.1 MBps, the OCZ Vertex 4 took fourth place at 449.4 MBps, and the 240GB Corsair Neutron finished a rather distant fifth at 414.3 MBps.

The Kingston HyperX was the most capable of the SandForce-based drives, posting a combined read/write rate of 407 MBps. The 240GB SanDisk Extreme finished next at 385.8 MBps, followed by the 240GB Intel 335 Series at 368.4 MBps.

To establish a baseline, we also tested an older SSD (a 90GB Corsair Force Series 3) and two mechanical hard drives: Seagate's Barracuda 7200.12 and Western Digital's VelociRaptor, both of which offer capacity that no current SSD can match: 1TB. The WD VelociRaptor is a very fast enterprise-class hard drive that spins its platters at 10,000 rpm. Note, however, that the Corsair and Seagate products do not represent the respective manufacturers' latest and greatest technology; we selected them as representative of the boot drives that consumers might be upgrading from. The Seagate 7200.12, for instance, has half as much cache as the newer 7200.14 model with the same total capacity. And the Corsair drive uses slower asynchronous NAND paired with a SandForce 2200 controller that predates the SandForce 2281 used in the newer drives we reviewed.

On the next page, I'll tackle the issue of pricing, bundles, and the bottom line.

Price

Though you'll see the manufacturer's suggested retail price quoted in our charts, it's not always indicative of how much you'll pay. Some vendors provide MSRPs that are actually street prices, while other vendors offer loftier MSRPs that end up being heavily discounted at retail. The 240GB SanDisk Extreme, for example, is list priced at $399, but we saw it at several online retailers for much less than half that amount. On the other hand, Intel priced its 335 series model at $184, but that drive was selling for more at several online retailers.

Based on street prices, the price per gigabyte ranged from about 69 cents to $1.08 per gigabyte for the 240/256GB models we reviewed. Although that's expensive compared with the 6 cents per gigabyte the Seagate hard drive fetches, or the 24 cents per gigabyte that WD's VelociRaptor commands, so is a Ferrari compared with a Volkswagen.

Bundles

Be aware of what comes in the box with the drive you choose. At a minimum, you should get a bracket and screws that let you adapt the 2.5-inch drive to a 3.5-inch bay. Some manufacturers go further and offer cloning software so that you can easily migrate your operating system and software environment from your old drive to the new one. Some manufacturers sell drives under different SKUs, one with just the drive and others with the drive plus accessories. Be sure to make apples-to-apples comparisons when you're shopping.

The bottom line

Speed is the primary motivation for upgrading to an SSD, so I recommend skipping over the bargain drives in favor of what you really want. The lone exception to that recommendation is for a laptop that has only a SATA 3-gbps interface. In that case, you should still stay away from bargain-bin drives, but make your choice based on price per gigabyte. If you're upgrading your laptop, be mindful of drive height: Some drives are 9mm high, and many thin-and-light portables can accommodate only 7mm drives.

We reviewed seven of the very latest SSDs for this roundup. The competition was tight, but one drive managed to outperform the rest of the field. You'll find links to our reviews below and after the jump!

Corsair Neutron (240GB): The middle of the road

Corsair's move to the Link A Media LM87800 controller has been a good thing. The Neutron GTX performs better thanks to its faster toggle-mode NAND, but the Neutron with its synchronous MLC NAND is still a very fast drive--fast enough to take the fifth spot among some very tough competition in our roundup.

Corsair's move to the Link A Media LM87800 controller has paid dividends. Though not quite as fast as the Samsung 840 Pro or the OCZ Vector, the Neutron GTX beat out the OCZ Vertex 4 to take third place overall.

Kingston's HyperX 3K was the best performer among the SandForce SF-2281 drives in our December 2012 roundup, by a fair margin: It took the sixth spot in overall performance. Kingston somehow managed to squeeze significantly better write performance out of this controller than the other vendors using the same part.

OCZ's latest drive, the Vector, utilizes the company's new IndiLinx Barefoot 3 controller in conjunction with synchronous MLC NAND. Said NAND is rated for 550-MBps sequential writing and 530-MBps writing, as well as for 95,000/100,000, 4KB write/read operations per second. Whatever the numbers, the Vector is fast.